The present invention relates to a method for manufacturing a package for packaging food products and to an apparatus for executing the method.
In conventional packagings of food products, particularly biscuits or crispbread slices arranged in a stack so as to form a pack, the enclosure is constituted by a package composed of an outer sheet of heat-sealable material and of an inner sheet made of paper-like material. The inner sheet has a smooth face and a corrugated (undulated) face comprising a plurality of small parallel folds having a sinusoidal orientation.
Within current packaging methods, the inner sheet is wrapped around the products so that the undulated face remains in contact with the products and the smooth face is in contact with the heat-sealable sheet, which wraps around it and covers it externally.
The package is closed by mating and mutually heat-sealing two border flaps of the outer sheet. Clearly, if the sheets are obtained by cropping films unwound from reels, in order to allow the border flaps of the outer sheet to make contact with each other in order to be heat-sealed together, the portion of the inner sheet that would otherwise become interposed between the two overlapping flaps of the outer sheet must be removed beforehand.
In any case, with known methods there are heat-sealing problems, since the pressure required to join the flaps of the outer sheet is applied against the product and cannot exceed certain limits in order to avoid damage to the product; moreover, the irregularities of the product produce an irregular heat-sealing line, in that loosely heat-sealed regions can be interposed between regions where the heat seal is scarcely reliable.
The looseness of the heat seal can make the packaging permeable to external agents and can compromise the integrity of the contained product.
The aim of the present invention is to provide a newly conceived method that allows to obviate the above noted drawbacks in the packaging of products in an enclosure constituted by a package composed of a heat-sealable outer sheet and of an inner sheet which has a smooth face and an undulated face.
In particular, the method must be able to ensure the hermetic tightness of the packaging without damaging the products even in the case of delicate products.
This aim is achieved with a method for manufacturing a package for packaging food products composed of an outer sheet made of heat-sealable material and of an inner sheet which has a smooth face in contact with said outer sheet and an undulated face, said sheets being cut from two respective outer and inner films unwound from reels, said outer film being wider than said inner film transversely to the unwinding direction, said method being characterized in that it comprises the steps of:
coupling said inner film to said outer film so as to form two lateral borders of said outer film left exposed by said inner film;
unwinding a length of said films from said reels;
making one film slide with respect to the other, parallel to said lateral borders, up to a staggered position, in which said inner film leaves exposed an end portion of said outer film which has a preset height and is perpendicular to said lateral borders;
cropping both films in said staggered position, so as to form said outer and inner sheets having two borders which are superimposed and two borders in which the inner sheet border leaves exposed said end portion of said outer film;
moving one sheet with respect to the other by an extent which is smaller than the height of said end portion, so as to form a package in which the inner sheet is centered on the outer sheet, so as to form two transverse borders which are lower than said end portion.
Within this aim, an object of the present invention is to provide an apparatus for executing the method whose characteristics are defined in the appended claims.
Another object of the present invention is to provide an apparatus that can be used in conventional packaging machines affected by the problem of insufficient hermetic closure of the packagings.